At the Hot Chips 2010 conference, IBM announced their upcoming z196 CPU, which is really, really fast. How fast? Fastest chip in the world fast. Intended for Z-series mainframe computers, the Z196 has a clock speed of 5.2GHz. Measuring just 512 square millimeters, the Z196 is fabricated on 45nm PD SOI technology, and on its surface contains almost one and a half billion transistors. My... Processor is bigger than yours.

It is not that a computer is as fast as it slowest component. The whole point of computer architecture is to make the common case fast. Veeeeery different.

So yeah, the booting speeds may have not progressed that much since they are constrained to the speed of the disk subsystem, which indeed is quite slow. But booting up is not the common case, is it? Running code is. And for the most part, most modern computers tend to utilize their processors rather well, try running a modern game on an old P3. This like databases etc are obviously more sensitive to I/O, but the machines used to run them are not necessarily comparable to a modern single user PC.